The present invention relates to a variable-capacity radial turbine which is capable of varying the size of an inlet of a turbine scroll passage, and which is especially suitable for a turbocharger of an internal combustion engine.
There is known a turbine of a turbocharger whose scroll passage is divided into two parallel scroll passages. One scroll passage is closed by a valve in a certain engine operating condition. Both scroll passages have inner side apertures opening toward the outer periphery of the turbine wheel. However, this scroll design causes a reduction of the turbine efficiency. When one passage is closed by the valve, there is formed a dead fluid zone in the closed passage. In this scroll design, the thus formed dead fluid zone is disturbed by the fluid moving around the turbine wheel, as explained more in detail later, so that the energy of the fluid is lost in the closed passage, and the turbine efficiency is reduced.